Extreme events will adversely affect water resources
Water availability and recharge are expected to be highly vulnerable to climate change. Fluctuation in rainfall will lead to instability in the country's water supply. Besides, climate change may also worsen water pollution.
According to M Lal of Centre for Atmospheric Sciences, iit , Delhi, Indian winters may experience a decline of five to 25 per cent in rainfall. This could lead to drought during dry summer months.
Lal predicts that the date of the onset of the summer monsoon over central India could become more variable in future. More intense rainfall spells are projected in a warmer atmosphere.
If rainfall decreases, water flow of rain-fed rivers will decrease. This will affect groundwater recharge (see graph: Erratic rains) .
Increase in rainfall might aggravate flood situations, bringing destruction and disease.
Since 1871, at least half the severe failures of the Indian summer monsoons have occurred in years of El Nio events. With increasing global temperatures, El Nio events are becoming more frequent and a higher frequency of drought conditions in some parts of India may follow.
A rise in sea surface temperatures may be accompanied by an increase in tropical cyclone intensities. According to ipcc, the intensity may go up by 10-20 per cent in the event of a 2-4 c increase in sea surface temperature leading to storm surges along the eastern coast of India.
The Himalayan glaciers, which feed many north Indian rivers and are the largest body of ice outside the polar regions, have been shrinking at an accelerated rate. According to Worldwatch, a us -based organisation, about 2,000 glaciers in the eastern Himalaya have completely disappeared in the last century. The Pindari glacier is receding at a rate of 13 metre a year while the Gangotri glacier is retreating at an annual rate of 30 metre. Warming is likely to increase the melting far more rapidly than accumulation of snow.
Glacial melt is expected to increase under changed climatic conditions which will lead to an increase in summer flows in some river systems for a few decades followed by a reduction in flow as glaciers disappear. As the rate of glacier melting gets higher, flash floods can be expected.
Rivers provide India with hydropower. The last decade has seen rapid deforestation, change in agricultural practices and urbanisation in mountainous region. This has led to frequent hydrological disasters, change in rainfall and runoff, extensive reservoir sedimentation and pollution of lakes. Global warming poses an additional threat to this region, which can harm power production.
Most of the Himalayan glaciers depend on both summer and winter precipitation, making them more sensitive to temperature variations than any other glaciers. Intense rainfall enhances melting of glaciers and late snowfall in winters does not give enough time for ice-formation. An intensified monsoon and high temperatures thus lead to retreating and thinning of glaciers, increasing the risk of flash floods.
River deltas will see incursion of salt water as sea levels rise affecting agriculture.
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